Running very rich - running out of options

[kblackav8or]

I have posts scattered around on this because so far I am at a loss. About a month ago got a CEL. Scanned it, called for bank 2 O2 Sensor. Replaced, reset the computer, went on our merry way. Not so fast, it is back again so I got under there, visually checked wiring, all looks fine, was a little oily so I cleaned things up a bit, flushed out the connector and put in some dielectric compound. Still runs horrible. Cleaned maf, IAC, unplugged, plugged back in, responded like they were working. Runs fine at WOT but misses like it is only running on 4cyl the rest of the time. I have a EGR DPFE on order thinking it might be that, tried running with it electrically disconnected, seemed to run better then ran worse. Running so bad right now it can't really be trusted. So did I kill an O2 sensor in 3 weeks? Could it be the fuel pressure damper (read some threads on regulators but not the damper). Can I bypass the DPFE for now or trick it into running OK until the new one arrives? If it isn't fixed by Friday after I parts swap some more, it is headed for the shop. Any help or guidance is appreciated.
Thanks.

 

[Runnin'OnEmpty]

K8, is it possible you installed the new O2 sensor in the wrong bank?
Bank 2 is the driver's side on our Explorers.

Are there any other codes?

 

[410Fortune]

Also a 02 sensor reading rich does not mean it needs a new 02 sensor, it means the 02 sensor is reading rich.

How many miles are on this 2000 truck and is this a V6 or V8?

Did you ever clear the memory after installing the new sensor, cleaning the MAS and the IAC?

You can determine if it is the fuel pressure and leak down test by doing a fuel pressure test at the fuel rail

it could be a simple spark plug or spark plug wire or similar (something simple)
if the EGR system was bad you would most likely have an EGR code, same is true for any emissions sensor.

Could this truck have an exhaust leak?

I vote you quit throwing sensors and $$$ at it, and do some testing.

 

[kblackav8or]

I replaced the drivers side with a Bosch O2 sensor about 14 August when this first started. I had also cleaned the other stuff, IAC, MAF etc. at the same time so it should have been fixed. Now I have the same code of no switching signal bank 2 O2 sensor. It runs rich and like crap unless it is WOT. Seems like it is running on 4cyl some of the time. The fact it runs great at WOT tells me it isn't wires or plugs or that periodically it runs fine anyway. I just cleaned the O2 sensor connector again last night and it didnt' make any difference. I looked at the harness it it looks like new and doesn't have any rub marks or burns or anything like that. I may try swapping out a sensor from side to side to see if it makes a difference. It is a V8 5.0 with about 53,000 on it. I have not gone so far as to disconnect the battery yet but did clear the stuff with a scanner. I don't think it has an exhaust leak. If it has a cracked manifold it will have torque masters to replace what is on there. I have an entire fuel rail with injectors and the damper on it I got cheap off ebay that should be here in a day or so. Does that damper thing just unscrew or how does it come off? Could it be the in tank fuel pump?

 

[410Fortune]

fuel pressure test will tell you if its the fuel system.
I am not sure if they switched the 5.0L system in 98 to the returnless style fuel rail system like they did with the V6's. I doubt they did on the 5.0L's but I just dont know. Both on my 96 truck and my 97.5 5.0L engine have the return style fuel rail so i assume the 5.0L was this way until production was stopped in 01


When I had a similar code, and swapping 02 sensors did nothing, I found one of the 3 pins inside the 02 sensor connector was pushed into th eplug, so it was not making contact.
Basically what your code is telling me is the computer is not getting feed back from thios 02 sensor, so if the sensor checks out, then its the wiring from computer to sensor. Also make sure you are messing with the correct sensor, bank 1 I believe (from memory here) on the 5.0L trucks is passenger side, drivers is bank 2./

The wires leave the computer and then are routed down to the trans,they connect to the trans harness through the big square plug on the D side of the trans, then to the 3 02 connectors on top of the trans (this is for 3 of the sensors, obviously the bank 2 sensor 1 plug is mounted on the d side of the trans bell housing, the green once that is simple to access)

The way to know for sure (to check the wiring from PCM to the 02 sensor) is to pull the plug off the computer and use a multimeter to check continuity between the appropriate pin to the 02 sensor plug itself.....kind of a PITA with the computer mounted in the cowl and the 3 02 sensor plugs on top of the transmission (access through the access panel under the center console in your truck), but at least doing this test will eliminate the wiring as your problem.
As long as you have replaced the correct sensor, then the wiring is the next thing to rule out.

As far as the FPR (fuel pressure regulator) being the cause or a weak fuel pump, a simple fuel pressure test will eliminate that as the cause, or pin point it immediatley.

 

[Turdle]

Check very closely for vacuum-intake leaks. The pcv fitting comes to mind, maybe the valve is loose?

 

[410Fortune]

what exactly was the code?

no switching signal bank 2 O2 sensor

An intake leak, or fuel system problem would not explain the 02 sensor not talking to the PCM as you mentioned, this points to a failed 02 sensor or the wiring to said sensor, aslo did it say bank 2 sensor 1 or sensor 2?
Sensor 1 is the main 02 sensor, bank 2 sensor 2 is the catalyst montor sensor.

 

[Turdle]

I presumed it was a not switching code

my bad

 

[kblackav8or]

I think it was 1149 or 1151. It was for the #2 bank heated O2 sensor not switching. I have plugged and unplugged it a couple times. I don't have my own scanner so I am going by memory. I looked at the pins last night, all clean and exposed. The computer is actually inside the firewall. Not sure how difficult it would be to extract but getting to the pins wouldn't be too bad. Now getting both ends contacted by myself would be pretty impressive I would think. I do have a factory wiring manual so it wouldn't be too much of a stretch to find and test the pins. I have no reason to suspect that just yet. I will look for more vacuum leaks. I tried a little bit yesterday with some propane but didn't find anything obvious. I have a PCV valve on order with the EGR sensor widget.

 

[410Fortune]

1151
Lack Of HO2S21 Switches - Sensor Indicates Lean

I show nothing for 1149


All 4 02 sensors are heated on your truck I believe.

I believe if you decipher HO2S21
Heated 02 Sensor 2 bank 1 right?
and the code is not lack of switching (would incdicate no communication) its switching indicates lean.

But the code is lean, are you sure its running rich?

Is 1151 the right code? very important...

 

[Turdle]

And with the stumbly idle-low rpm performance, no egr codes, I suspect vacuum leak.

Although
An exhaust leak would indicate lean perhaps, and cause the PCM to richen the mixture resulting in a rich odor??????

 

[kblackav8or]

P1152. I just double checked where I had posted on it before. I just yanked the PCV. I am used to the ones where the check ball widget moves freely. This one doesn't. Could that be the problem? I have the vacuum to the manifold plugged right now and drove it around the block. It also seems like the PCV doesn't fit real tight in the gromet. Could it be?

 

[410Fortune]

PCV does not fit very tight from the factory, plus that sucker is hard to see on the 5.0L

What do you mean plugged?
check ball in the PCV should rattle

 

[Turdle]

How did he get that so fast?

 

[kblackav8or]

OK so I ran back outside and I put a bolt in the vac line to the manifold IE plugged. The PCV doesn't seem right to me, moving part doesn't seem to move properly and even after liberal use of Ford carb cleaner and some brake clean hasn't helped as much as I would have liked. I had a friend on the phone who said to try some brake clean around the upper manifold gasket. No difference. He says they occasionally fail leading to a leak. I drove it a second time with the vacuum line blocked after I reset the CEL by disconnecting the battery and it ran better. Idling at 650 though not totally smooth, much better then before. Power is good, no stumbling, CEL has not come back on. So it would seem to be vacuum related since messing with vacuum stuff seems to fix or help the problem significantly. Right now the PCV is in the manifold and the hose is plugged with a bolt to close that vacuum path. The crankcase can still vent and a day without a functioning PCV shouldn't cause too much trouble especially if it is running better. For the longest time I couldn't even find the darn PCV on it. Until I get a new one in there I won't declare victory and hopefully I can turn off my order of that DPFE.

 

[410Fortune]

if your DPFE was bad you would have a EGR code IMO

Have you considered getting a gasket set and re-sealing from the heads up?
removing the upper intake (at least) is a great way to find the condition of all the gaskets, vacuum lines, etc
And to ensure the PCV is seated properly inside its grommet

 

[kblackav8or]

Ok it was driven maybe 50 miles today with the PCV blocked. Most of the day it was fine. Then I started missing and chugging losing power and generally running like crap. My wife was driving - her rig. CEL is back on. I am just about ready to take it in and throw in the towel.

 

[Turdle]

Just a long shot
Fuel filter?

 

[kblackav8or]

Changed fuel filter last Friday thinking the same thing. Made no difference. Air filter is good. I just came home with an upper intake gasket, a PCV and another O2 sensor . If all else fails the O2 sensor will get used on another project I am working on so it isn't a total loss. I have one spare (minus the plug) lying around. What is most disturbing is that it will run fine for probably close to an hour and then start running like crap even with the PCV feed closed off to eliminate it as a source of a vac leak. After this if it doesn't fix the problem I will be at a loss for what to do next.

 

[chris chick]

I'm having the same problem and seeing you guys stumble through all the possible fixes makes me wonder if perhaps this is one time where a trip to the dealership wouldn't be such a bad thing???

chris